Randomly looped filamentary blend



Nov. 26, 1963 c. BOYER 3,111,805

RANDOMLY LOOPED FILAMENTARY BLEND Filed Jan. 28, 1959 IN VENTOR CLARENCE BOYER ATTORNEY United States Patent Ofi 3,1 l 1,8 Patented Nov. 26, 1963 ice 3,111,805 RANDEBMLY LGQPED FZLAMENTARY BLEND Clarence Boyer, Swarthniore, Ea, assignor to E. H. du Pont de Nemours and Company, Wilmington, Del, a corporation at Delaware Filed .lan. 28, 1959, Ser. No. 750,551 6 Claims. (Ci. 57-140) This invention relates to yarn-like structures of synthetic filaments. More particularly, it relates to improved synthetic elastomeric yarns having wool-like properties which are comprised of a plurality of continuous filaments.

In the textile art it has been conventional to prepare elastomeric thread or yarn by wrapping a core of a rubber filament with a continuous filament or a spun yarn. This wrapped core is then combined with another layer of some filamentary material. Products so prepared have been limited to rather high denier due to the use of a solid elastomeric core such as rubber and the wrappings on the core. Such products are also undesirable since separation or disintegration of the wrapping and subsequent exposure of the elastomeric core often occurs. In addition, the process used for making yarns or" this type is quite involved and costly due to the many plying, winding, and twisting operations that are required. The use of yarns spun from staple fibers which is necessary in order to produce yarns having wool-like properties also greatly adds to their cost.

It is therefore, an obiect of this invention to provide continuous filament elastic yarn having the appearance of a spun staple yarn. It is another object of this invention to provide yarns which when embodied in fabrics will provide bulk and elasticity. A further object of this invention is to provide a novel process for preparing such yarns. Further objects will appear hereinafter.

The objects of this invention are accomplished by providing a composite filamentary structure comprised of at least two continuous fiber components disposed in eccentric relationship to one another, one of said components being a synthetic polymeric fiber capable of being drawn at least two times its original length and having a maximum breaking elongation of less than 80% and an initial modulus from about to about 200 grams per denier, the other component being a synthetic elastom ric polymer having an elongation of at least i00% and an initial modulus from about 0.01 to about 0.5 gram per denier. Upon being drawn and relaxed the components substantially separate into separate fiber structures. The elastomeric fibers of the structure remain essentially straight and the other fibers become randomly looped about the elastomeric fibers. The filaments comprising the structure of this invention, although having substantially zero twist, cling to each other to provide a yarn which has high bulk as well as elasticity.

The products of this invention are prepared by a process which comprises simultaneously extruding at least two fiber-forming compositions, of the type described above, in side-by-side relationship to form a composite structure in which the separate compositions are in eccentric relationship to each other, drawing the composite structure at least about two times its original length, and thereafter relaxing the drawn structure. Due to the different response to the drawing and relaxing steps, the hard filaments substantially separate from the elastic filaments. Since the amount of irreversible elongation achieved in drawing the hard filaments is greatly in excess of that achieved in the elastic filaments, upon release of tension after drawing, the hard filaments buckle and loop about each other and the essentially straight elastic filaments in a random fashion. Surprisingly, it has been found that when the two fiber-forming compositions are extruded so that there is some adhesion to each other, ease of handling of the structure results with the elastic and hard filaments substantially separating during the drawing and relaxing steps.-

The term hard fibers as used herein is applied to those fibers having a maximum elongation of before rupture or breaking, i.e., elongation which is substantially recoverable upon release of tension. The hard fibers pre- {erred in this invention will usually stretch no more than about 20% to 40%, and will have an initial modulus of between about 18 and grams per denier. Elongation is distinguished from the permanent extension of the fibers produced by drawing as set forth above. The as-spun hard fibers useful in the present invention are those capable of being drawn, i.e., being permanently extended, at temperatures between about 50 and 150 C. from about two to ten or more times their original length.

The term elastorner as used herein has the meaning conventionally given to that term in the art. Filaments prepared from synthetic elastomeric polymer are characterized by having a recoverable elongation of from about to about 800% before breaking, and preferabiy have a modulus, i.e., stress required to stretch the filament 100% of from about 0.01 to about 0.1 gram per denier. Such fibers are characterized by a high tensile recovery, i.e., recovery to the original untensioned condition. Elastomers which are suitable for use in the present invention are those which are prepared from substantially linear elastomeric polymers which may be extended in filamentary form and capable of being elongated at least 100% before breaking and are not appreciably permanently elongated when stretched at temperatures from 50 C. to C.

By relaxing as used herein is meant substantially releasing tension on the drawn structure accompanied by a heat treatment as described more fully later herein.

The hard fiber component of the yarn may be selected from any of those fiber-forming polymers which are capable of being spun into filaments which can be drawn at least two times their original length at a temperature from about 50 C. to about 150 C. Such polymers in clude various types of polyesters, polyamides, polyesteramides, polyurethanes, polyureas, and polyhydrocarbons, which will be further described later herein.

The elastomeric component of the products of this invention comprises from about 5% to about 70% by weight of the yarn, with products having from about 20% to about 50% of the elastomer being preferred. Polymers suitable for use as the elastomeric component of the prodnets of this invention are those which may be extruded in filamentary form. Among these polymers are the segmented or block copolymers which are elastomeric in nature, condensation elastoniers, and addition elastomeric polymers which will be further described later herein. The preferred segmented elastomers are those containing a bis-ureylene segment alternating with segments of a low melting polyether or polyester. Such elastomers are obtained by coupling difunctional macromolecular intermediates with hydrazine or its derivatives, and have the general formula HOXXO in which R is a kylene, Ar and Ar are arylene, z is an integer not greater than 3, n is of a value to impart a molecular weight of greater than 300 to the group within the brackets, X and X are selected from the group consisting of hydrogen and monovalent hydrocarbon radicals, and y is an integer greater than zero. These elastorners are more fully described in the copending application of Frankenburg & Frazer, US. Serial No. 556,071, filed December 29, 1955 and now US. Patent No. 2,957,- 852.

In practicing this invention the elastomeric polymer and the polymer yielding hard fibers are preferably prepared so that upon extrusion in side-by-side relationship the two materials have sutllcient adhesion to form an asspun filament that comprises an essentially composite structure. At the same time such adhesion must not be so great as to prevent splitting of the fiber component into separate elastic and hard fibers during the subsequent drawing and relaxation steps.

The adhesion of the two polymer candidates can be readily ascertained by casting films of the polymers in a similar relationship to that obtained in the extrusion step. The determination of adhesion between the two films can be made by drawing the if the desired polymer combination does not have the optimum adhesion characteristics, adhesion can be increased by blending in a small amount, for example 110%, of either the hard or elastomeric polymer with the other polymer. If the adhesion appears to be too great, one polymer might be modified by incorporating with it from about 520% of another monomer whose homopolymer has poor adhesion for the other polymer.

In the process of this invention an elastomer which is substantially non-drawable, that is the elastomer, when extended and released, quickly recovers its full original length, is preferred. However, elastomers which have a certain amount of non-reversible elongation may be used provided the draw ratio of the composite structure exceeds the maximum permanent, i.e., non-reversible, elongation of the elastomer component by at least 100%. This is necessary in order to produce bulking of the elastic yarn.

The spinning or extrusion process selected will depend on the type of polymer being extruded. The process described by Rothrock in US. Patent 2,706,674 may be used for melt or plasticized melt spinning. Dry or .vet spinning, or a combination, e.g., melt and dry spinning, can be used for certain combinations of polymers. In the latter case the residual solvent in the dry spun polymer can be readily extracted during subse uent processing. A spinneret of the type described in the copending application of Taylor, application Serial No. 771,677, filed November 3, 1958 and now US. Patent No. 3,038,- 237, may be used.

Although elastomers which do not require curing or vulcanization are preferred, the present process lends itself to the use of elastorners which require curing. If such elastomeric polymers are used, the curing step to develop and fix the elasticity of the fiber must be accomplished prior to drawing the composite structure. This may be conveniently achieved by the addition of curing agents such as magnesium oxide or sulfur, the latter preferably in combination with accelerators such as Z-mercaptobenzothiazole or di-Z-benzothiazyl disulfide, etc., plus heating the structure at a temperature of from about 100 to about 150 C. immediately following the extrusion step. When using an elastomer such as a silicone rubber in combination with a hard fiber-forming polymer, for example a polyamide, the elastorner may be cured before drawing by subjecting it to electronic radiation.

The drawing conditions used in the process of this invention will be primarily determined by the character of the hard fiber used. The temperature used may vary from cold drawing temperatures, that is 25 to 50 C.,

to temperatures approaching the melting point of the lower melting polymer in the composite structure.

in general, conditions during the relaxation step will be selected to take advantage of the properties of the hard ilber component. For example, polymers containing at least acrylonitrile, which are particularly desirable as the hard fiber component due to their resistance to chemical reagents, ultraviolet light degradation, and their outstanding physical properties such as wool-like hand, when drawn from two to ten times their original length, are known to possess a certain amount of residual shrinkage which may be developed by a hot, wet treatment. This residual shrinkage may be utilized in a further relaxation step after being woven into a fabric to give even greater bulking to the finished product.

An embodiment of this invention is illustrated in the accompanying drawings in which FIGURE 1 is a greatly enlarged cross-sectional view of the as-spun composite filamentary structure of this invention; and FIGURE 2 is an enlarged eleva-tional view of the composite filamentary structure of FIGURE 1 after it has been drawn and relaxed. In FIGURE 1 the composite structure consists of approximately 50% of the hard fiber, illustrated by the clear component, and about 50% of the elastomer, illustrated by the cross-hatched component. When the structure is drawn and relaxed, the components substantially separate from each other as shown in FIGURE 2 with the hard fibers becoming randomly looped about the elastomeric fibers.

This invention will be further illustrated but is not intended to be limited by the following examples in which parts and percentages are by Weight unless otherwise indicated. In the examples the term intrinsic viscosity with the symbol (n) is used to indicate the value of 1n(n) at the ordinate axis intercept (i.e., when 0 equals 0) in a graph of i.e., the inherent viscosity, as the ordinate with 0 values (grains per ml. of solution) as abscissas; (n) is the symbol for the relative viscosity, which is the ratio of the flow times in a visoosimeter of a polymer solution and the solvent; In is the logarithm to the base e. Stress decay is the percent loss in stress in a yarn one minute after it has been elongated to 50% at a rate of 100% per minute. Tensile recovery is the percentage return to the original length within one minute after the tension has been released from a sample which has been elongated 50% at the rate of 100% per minute and held at 50% elongation for one minute.

EXAMPLE I A segmented condensation elastomer (hereafter designated elastomer A) is prepared by condensing poly-tetramethylene oxide) glycol (one mol) having a mol cular weight of 1,000 with one-half mol of toluene diisocyanate. The resulting mol of dimer having hydroxyl end groups is then reacted with two mols of methylene bis(4-phenyl isocyanate). The resulting one mol of a polyether diurethane having isocyanate terminal groups is then reacted with one mol of hydrazine monohydrate in N,N- dimethyl-torma-mide (DMF) to produce a copolymer with an inherent viscosity of 1.6 as measured in hexamethyl phosphoramide solution.

A spinning solution containing 20% of the above polymer and 5% of N,N-diethylaminoethyl methacrylate (based on polymer) and 5% of TiO (based on polymer) in DMF is prepared. This solution and a 27% solution in DMF of the copolymer aorylonitrile/methyl acrylate/ styrene sulfonic acid (93.6/6.0/0.4), having an intrinsic viscosity of 1.5, are simultaneously extruded through common orifices in a spinneret similar to that described in copending application Serial No. 771,677, filed Novemher 3, 1958 and now US. Patent No. 3,038,237, containing 40 orifices of 0.175 inch in diameter into a dry spinning cell With a concurrent flow of cell gas. The resulting composite filaments are wound up at 300 yards per minute. The polymer solutions are extruded at 90 C. The temperature of the cell gas is 300 C. as it enters the spinning cell around the spinneret. The temperature of the jacket of the cell wall is 200 C.

The as-spun yarn (420 total denier) is a straight nonelastic yarn composed of composite filaments containing 50% of the acrylonitrile copolymer and 50% of Elastomer A by weight. A cross-section of the as-spun yarn is shown in FIGURE 1.

The as-spun yarn is drawn 8X, i.e., eight times its original length, through baths of water at 95 C. (which also extracted the residual DMF in the yarn) and through a steam cell in sequence. The drawn yarn is then led through a cell containing steam at atmospheric pressure with the feed rolls to and delivery rolls from the steam cell adjusted to permit a 50% shrinkage in the length of the yarn and relax the acrylonitrile copolymer portion. The relaxed yarn is run over a finish roll applying 2% to 5% of a finish comprising a water emulsion of cetyl alcohol, stearic acid, and lanolin. The yarn is then wound onto packages. An elevational view of a drawn and relaxed yarn similar to that obtained is shown in FIGURE 2. The drawing and relaxing process results in the splitting apart of the hard fiber and the elastomer fiber as evidenced by the relatively straight elastomer fibers and the randomly looped hard fibers in the figure. It is found that the filaments of elastomer A undergo a 1.7 net draw when drawn 8x and relaxed in steam or boili-ng water, i.e., they have a final untensioned length that is 1.7 times their original length.

The filaments spun from elastomer A above have 21 Item h is prepared by blending elastomer A staple (six denier per filament, two inches long) and staple (one denier per filament, one and one-half inches long) of the acrylonitrile polymer of Example I in the ratio of 20/80,

5 respectively, and spinning a staple yarn. Other work indicates that cotton counts of 20 or 30 (i.e., deniers of 266 or 177) appear to be the minimum fineness, after scouring that can be prepared by the latter two methods.

A plain fabric is woven of the yarn of item b. The

10 fabric after the usual finishing and scouring procedures is moderately elastic (100% elongation), has a uniform suede-like appearance with a pleasing soft velvet-like hand and has excellent covering power. It is well adapted for the fabrication of form-fitting garments, evening gloves,

and the like.

FIGURE 2 which shows a preferred species of the invention, illustrates the feature of items a to 1, namely the crimped or bulky character of the entangled loops of the hard fiber. It is considered that this crimp accounts for the unusual hand of fabrics made from such yarns. The

figure clearly shows the features common to all yarns of this invention, namely the intimate mixture of the substantially straight elastomer filaments and the randomly looped hard fibers. It is to be noted that the hard fibers are not mereiy twisted about the elastic filaments but are looped about the hard fibers in a random fashion. The finished yarns have substantially zero twist.

The individual hard fibers and elastomer fibers in the relaxed yarn of item c have deniers of about 1.1 and 1.5,

respectively. The individual hard fibers and elastomer and hard fiber components do not tend to bunch together.

Table Yarns of This Invention Control Yarns Item I: b c i (l e l f g h As-Spun yam denier/filaments.. 100/10 175/10 250/20 420/20 670 Draw ratio 5. 5X 8X 8X 8X 8X Relaxation, perccnt 53 56 00 60 Residual Shrinkage 30 34 34 32 Properties after boil-01f: 1

Denierls cotton count 68/18 06/55 163/33 257/21 425/13 Tenacity, grid/Elongation, percent. 0 8/168 0. 7/240 0. 6/270 0. 6/288 0. 5/285 Tcnancity at 200% Elongation, g.p.d 0. 33 0. 24 0.17 0.17 Tensile Recovery from 50% Elongation,

percent i 81 88 8G $0 83 77 Stress Decay at 50% Elongation, percent. 8. 9 13. 3 8. 3 8. 8 10. 1 10 0. 2 5. 2 Modulus, g.p.(l. calculated from lead at 50% elongation 0. 012 0. 014 0.013 0. 015 0. 015 0.012 0.001

1 For 20 minutes.

tenacity of 0.6 gram per denier, an elongation of 600%, EXAMPLE III an initial modulus of 0.05 gram per denier, stress decay of 6.5%, and tensile recovery from 50% elongation of Filaments spun from the acrylonitrile polymer of this example have the following properties after an 8X draw and relaxation: tenacity 5 grams per denier, elongation 17%, and modulus of gram-s per denier.

EXAMPLE II The following examples illustrate some of the physical properties of the yarns of this invention.

Items :2 to e, shown in the table which follows, are prepared as in Example I with the composite structure containing 75% of the acrylonitrile component and 25% of elastomer A. Item f is prepared in a similar manner and contains equal weights of both components. Different spinnerets and draw ratios are used to vary the samples.

Item g is prepared by spinning a sliver of the acrylonitrlle copolymer staple of Example I around a 150 denier monofil of elastomer A. The thread contained approximately 25% by weight of the elastomer.

Twenty percent (20%) solutions in DMF of elastomer A and 1a 94/ 6 acrylonitrile/methylacrylate copolymer are simultaneously extruded at C. through a spinneret similar to that used in Example I having 20 orifices 0.005

60 inch in diameter into a spinning cell, the oil heated walls ofwhich are maintained at 220 C. The yarn is wound up at 43 0 yards per minute. Nitrogen gas at 290 C. (0.5 pound/hour) enters the cell from around the spinneret. The as-spun yarn comprising composite filaments 65 of the two polymers in a 50/ 50 ratio is straight, non-elas- 75 by boiling in water for 20 minutes, fine intermingled loops of the hard fiber appear on the surface of the yarn, and

the presence of 0.15% 0.05% antimony oxide (based on weight of dimethyl teriephthalate plus the polyether) to an inherent viscosity of 7 the yarn shrinks in length about 70%, yielding an elastic yarn with the appearance and feel of a spun staple yarn.

Filaments prepared from the above acrylonitrile cpolyrner have a tenacity of 2.5 grams per denier, an elongation to break of 20%, and a modulus of 45 grams per denier after a X draw and relaxation.

The yarn, prepared as described above, is compared with a 34 filament (100 denier total) yarn of polyacrylonitrile filaments after both were boiled in water for 20 minutes. Skeins of the two yarns can be elongated 342% and 4%, respectively, of their initial length and both recover 81% of the elongated length, based on the elongation. The bulk of a yarn is measured by determining the amount of water the yarn retained after being immersed in water and allowed to drain free. The two yarns retain water to the extent of 500% and 270% of their dry weight, respectively.

Rib half-hose, 6 x 3 with 9 courses per inch, are knitted using the two yarn-s described above before boiling in water. After finishing, the control hose can be extended only 30% and have the typical continuous filament appearance. They have very poor covering power and are limp. The hose prepared from the yarn of this invention can be stretched 130%, have excellent covering power, and have a soft, pleasing hand similar to that found in spun-staple yarns.

EXAMPLE IV A wholly aromatic polyamide which affords a hard fiber is prepared by condensing a cold mixture of m-phenylene diamine in N,N'-dimethyiacetamide with isophthaloyl chloride. A molar quantity of calcium hydroxide is added to the reaction product to neutralize the hydrochloric acid formed as a by-product in this reaction. This solution containing 20% of the polyamide of inherent viscosity 1.8 as measured in dimethylacetamide is used below to provide the hard fiber component.

The above solution of the polyamide and a solution of elastomer A of Example I in DMF (20% solids) are simultaneously spun from a spinneret similar to that used in Example I by the wet spinning method into a coagulating bath at 50 C. comprising calcium chloride, dimethylacetamide and water, 10/ 30/ 60 parts by weight. The wet as-spun yarn, comprising composite filaments, the elastomer being present in an amount of about 25% by weight, is drawn 5 X through a 95 C. water bath and the yarn thereafter allowed to relax in a cell containing steam at atmospheric pressure. The drawn and relaxed yarn is a bulky, elastic yarn which resembles the product of Example I.

Yarn spun from relaxed, has a tenacity of 5 gation of 30%.

Similar results are obtained when the solution of polyamide is replaced with a 20% solution of polyvinyl chloride having an inherent viscosity of 1.5 as measured in cyclohexanone, and the same process is carried out.

EXAMPLE V An elastomeric, polyether ester is made by polymerizing 40 parts of dimethyl terephthalate, 60 parts of poly(tetramethylene oxide) glycol having a molecular weight of '1 560 and an excess of ethylene glycol by ester exchange in calcium acetate monohydrate and the above polyamide, drawn 5 and grams per denier and an elonl.0 as measured in a 60/ 40 mixture of phenol and tetrachlorethane.

Melts of the above elastomer and polycaprolacta-m, as

"the hard fiber component, are simultaneously extruded at polyamide looped and intermixed with the elastomer filaments. The elas-tomer. filaments. comprised 25 of the total weight of the yarn.

This example illustratesthe use of an elastomer that can be drawn. Homofilaments of the above elhstomer when drawn 6X retract to a net draw of 2 when relaxed in boiling water. The relaxed filaments have a tenacity of 040 gram per denier, an elongation of 350%, and a modulus of 0.13 gram per denier.

It will be apparent that the yarns of this invention may be used with or without relaxation in the production of fabrics. The bulk and elasticity of the product may be developed after fabrication by relaxing the fabricated article by scouring or other treatment in a hot, wet medium. lreferably, the yarn is relaxed, that is subjected to shrinking conditions, to relieve the strain effected by the drawing operation by treating it in hot or hot-wet atmosphere for a period of time from about 2 seconds to about 20 minutes before further processing. Generally, the temperature used must be above about 50 C. but below the melting point of the lowest melting polymeric constituent in the yarn. A temperature in the range from about 50 C. to about 150 C. may be conveniently used.

As previously indicated, for certain composite structures the relaxation of the drawn yarn need not be completed in one step. It may be preferable to partially relax the yarn to a sufficient degree to develop its elasticity and bull; while still retaining from about 10% to about 30% residual shrinkage to develop even more elasticity and bull; in the final product in a final relaxing step. The degree of bulking obtained in the final product will of course depend on the properties of both components.

As previously indicated, polymers suitable for use as a hard fiber component of the yarns in this invention may be found among many types of polymeric, fiber-forming materials. Condensation polymers such as polyesters, polyamides, or polyester amides as described in US. Patents 2,071,250, 2,071,253, 2,130,523, 2,130,948, 2,190,- 770, and 2,465,319, as Well as polyurethanes such as those described in U.S. Patent 2,731,446, and polyureas are satisfactory. Addition type polymers such as polyhydrocarbons, polyethers and those made from ethylenically unsaturated monomers such as acrylonitrile, vinyl chloride, vinylidene chloride, vinyl acetate, and their copolymers with each other and other copolymerizable monomers such as methyl acrylate, methyl methacrylate, N-vinyl pyrrolidone, may be used. Polymers containing or more acrylonitrile combined with numerous monomers including ethylenically unsaturated sulfonic acids such as the methallyl sulfonic acids and others as disclosed in US. Patents 2,527,300 and 2,601,256 which can be copolymerized with acrylonitrile as disclosed in Jacobson US. 2,436,926 and in Arnold US. 2,456,360 to produce copolymers are especially preferred.

Polymers suitable for use as the elastomer component of yarns of this invention may be found in many classes of polymers. Segmented (i.e., block copolymers) elastomers, which comprise the preferred class of polymers useful for this purpose, are prepared by starting with a low molecular weight polymer, i.e., one having a molecular weight in the range from about 700' to about 6000, that is difunctional and has terminal groups containing active hydrogen and reacting this difunctional polymer with a difunctional coreactive molecule. Mixtures of one or more aromatic dibasic acids (or their ester-forming derivatives) may be reacted with one or more difiunctional polyethers and one or more lower aliphatic glycols to form a useful elastomer. Alternatively, the difiunctional polymer containing active hydrogen may be reacted with a coreactive molecule to yield a new difiunctional intermediate having terminal groups capable of reacting with active hydrogen. Such intermediates are then coupled or chain-extended by reacting with compounds containing active hydrogen as for example, water, hydrazine, diamines and dibasic acids. The low molecular weight 9 Starting polymer may be a polyester or polyester amide or polyether and the coreactive small molecule, a diisocyanate.

US. 2,692,873 describes similar products in which the starting polyesters have been replaced by polyethers of a corresponding molecular weight range. A number of mace-molecular compounds, such as polyhydrocarbons, polyamides, polyurethanes, etc., with suitable molecular weights, melting point characteristics, and terminal groups, can serve as a starting point for preparing segmented elastomers of this type.

Other types of condensation elastomers are also suitable. US. 2,679,267 describes N-alkyl-substituted copolyamides which are highly elastic and have a suitable low modulus. A copolyamide of this type, obtained by reacting sebacic acid with a mixture of l'iexarnethylene-v diarnine, N -isobutylhexamethylenediamine, and N,N'-diisobutyihexarnethylenediamine, produces an elastorner which is particularly satisfactory for the purposes or this invention. US. 2,623,933 describes linear elastic copolyesters prepared by reacting glycols with a mixture of aromatic and acyclic dicanboxylic acids. Copolyrners prepared from ethylene glycol, terephthalic acid, and sebacic acid have been found to be particularly useful. Another class of useful condensation elastorners is described in Us. 2,430,860. The elastic polyarnides or" this patent are produced by reacting polycarbonamides with formaldehyde.

Suitable elastorners may be found among the fiberforming addition polymers such as, for example, copolymers of butadiene/styrene, butadiene/acrylonitrile and butadiene/Z-vinyl pyridine, polychlorobutadiene, copolyrners of isobutylene with small proportions of butadiene, chlorosulfonated polyethylene, copolymers of monochlorotrifiuoroethylene with vinylidene fluoride, and the like.

It will :be obvious to one skilled in the art that the nature of the finished product can be controlled to some extent by the amount and nature of twist applied to the yarn at various steps in this process. In the preferred process to make the preferred product, twist is not required to hold the composite yarn bundle together but it will be appreciated that depending on the adhesion of the components, a small amount, perhaps two to six turns per inch, may be desirable to aid in the processing of the as-spun, the drawn but unrelaxed, or the relaxed yarn.

It will also be appreciated by those skilled in the art that the ability to process such yarns can be changed or altered by the use of proper finishing agents.

The elastic yarn of this invention is of special advantage in that it has excellent elasticity, and has the appearance and hand of a spun yarn while retaining the economy of continuous filament yarns. Such yarns can be made in much finer counts than were heretofore commercially feasible. This enables new and novel fabrics to be made from such yarns. Jersey knitted fabrics and woven fabrics from the yarns of this invention have a clean, uniform appearance, a line, suede-like hand, and are moderately elastic. The fibers of this invention can be used in such items as mens half-hose, surgical hosiery, and in form-fitting garments of all types.

It will be apparent that many widely different embodiments of this invention may be made without departing from the spirit and scope thereof, and therefore it is not intended to be limited except as indicated in the appended claims.

l claim: 4

1. A composite elastic yarn comprised of at least two species of continuous fibers, said first species being hard fibers and said second species being eiastomeric fibers having an elongation of at least about 100%, said second species being essentially straight and said first species normally being randomly looped about said second species when said yarn is in an essentially untensioned condition and becoming straightened when said yarn is placed under tension.

2. The product of claim 1 wherein said elastomeric fibers comprise from about 5% to about by weight of said yarn.

3. The product of claim 1 wherein said elastomeric fibers are comprised of a linear segmented elastomer.

4. The product of claim 3 wherein said segmented elastorner is a synthetic polymer containing bis-ureylene segments alternating with segments of a low-melting polyether.

5. The product of claim 1 wherein said hard fibers are comprised of acrylonitrile.

6. A fabric comprised of the yarn of claim 1.

References Cited in the file of this patent UNITED STATES PATENTS 1,867,298 Zart July 12, 1932 1,976,201 Taylor Oct. 9, 1934 2,399,260 Taylor Apr. 30, 1946 2,439,814 Sisson Apr. 20, 1948 2,443,711 Sisson June 22, 1948 2,504,523 Harris et al Apr. 18, 1950 2,517,946 Von Kohorn Aug. 8, 1950 2,536,163 Feild et al Jan. 2. 1951 2,783,609 Ereen Mar. 5, 1957 2,979,883 Waltz Apr. 18, 1961 2,996,872 Porczynski Aug. 22, 1961 

1. A COMPOSITE ELASTIC YARN COMPRISED OF AT LEAST TWO SPECIES OF CONTINUOUS FIBERS, SAID FIRST SPECIES BEING HARD FIBERS AND SAID SECOND SPECIES BEING ELASTOMERIC FIBERS HAVING AN ELONGATION OF AT LEAST ABOUT 100%, SAID SECOND SPECIES BEING ESSENTIALLY STRAIGHT AND SAID FIRST SPECIES NORMALLY BEING RANDOMLY LOOPED ABOUT SAID SECOND SPECIES WHEN SAID YARN IS IN AN ESSENTIALLY UNTENSIONED CONDITION AND BECOMING STRAIGHTENED WHEN SAID YARN IS PLACED UNDER TENSION. 